For an electric car or a hybrid car in which a motor for driving a vehicle is driven by electric power from a power storage device represented by a secondary battery, a configuration for charging the power storage device with an external power supply has been proposed.
For example, Japanese Patent Laying-Open No. 11-164409 (Patent Document 1) discloses, as a method for controlling charge of a battery for an electric car, a configuration in which a junction box containing a contactor capable of disconnecting an electrical path is arranged between an external charger and a battery for motive power connected to each other through a charge plug and an auxiliary battery is charged by a DC/DC converter connected to a charger through the charge plug. According to Patent Document 1, when a voltage of the auxiliary battery attains to a prescribed reference value at the time point of lapse of a prescribed period of time for charging, the contactor in the junction box is set to the OFF state and the DC/DC converter is controlled to stop, so that waste of the charged battery for motive power can effectively be reduced.
In addition, Japanese Patent Laying-Open No. 2000-232737 (Patent Document 2) discloses a configuration for reliably stopping control of an inverter when a charge plug is pulled out of a socket, in a charging device for charging a secondary battery by converting an external AC current to DC power by using the inverter. Specifically, such a configuration that whether external electric power is supplied or not is determined based on comparison between a current input to the secondary battery and a control target value of the inverter and when it is determined that there is no external supply of electric power, the inverter is stopped to stop charging is disclosed.
Moreover, Japanese Patent Laying-Open No. 10-290534 (Patent Document 3) discloses a battery charging device for successively calculating a remaining capacity of a battery and automatically stopping charging when the remaining capacity attains to 100%. Specifically, when the remaining capacity attains to 100%, a contactor (a relay or a switch) arranged between a charger and the battery is opened even though a charge instruction switch is operated. Thus, overcharge of the battery and waste of electric power can be avoided.
Further, Japanese Patent Laying-Open No. 2004-289954 (Patent Document 4) discloses, as a power supply control device of a battery vehicle capable of achieving reduced current consumption while a key switch is turned off, a control configuration capable of reducing current consumption by turning off also a DC/DC converter for supplying power to a controller while the key switch is turned off. According to this power supply control device, when a charge plug is inserted in a charge connector, a relay contact is closed in response to a sensing signal from an AC detection circuit, so that power supply from the DC/DC converter to the controller is started and the controller can operate.
Japanese Patent Laying-Open No. 11-205909 (Patent Document 5) discloses a charging device for an electric car capable of checking an operation of a ground fault interrupter during charge of the electric car. According to this charging device for an electric car, during charging, a leakage test relay is closed to forcibly cause a short circuit and whether the leakage relay is disconnected or not is checked. After it is confirmed that a disconnection relay has been disconnected, a charge relay is closed and charging can be started.
Similarly, Japanese Patent Laying-Open No. 2000-354332 (Patent Document 6) discloses a configuration in which, in connecting a plug of a charging device to a socket for starting charging, leakage is technically caused by using a test circuit and charging is started on condition that a leakage detection circuit normally operates at this time. By doing so, such a defect as electric shock can be prevented and safety can be ensured.